GTE therapy is offered to all boys with the biochemical defect of ALD. This therapy reverses the principal biochemical abnormality, namely, the accumulation of very long chain fatty acids. We are encouraged by the fact that all the patients who were neurologically symptomatic at the beginning of therapy have remained so and that their brain MRI studies also have remained stable. Mean duration of therapy is 14 months. Longer followup is required for definitive conclusion.